title: Overexpression of PRMT6 does not suppress HIV-1 Tat transactivation in cells naturally lacking PRMT6.
abstract: BACKGROUND
  Protein arginine methyltransferase 6 (PRMT6) can methylate the HIV-1 Tat, Rev and nucleocapsid proteins in a manner that diminishes each of their functions in in vitro assays, and increases the stability of Tat in human cells. In this study, we explored the relationship between PRMT6 and HIV-1 Tat by determining the domains in each protein required for interaction.
  
  
  METHODS
  Through domain mapping and immunoprecipitation experiments, we determined that both the amino and carboxyl termini of PRMT6, and the activation domain within Tat are essential for interaction. Mutation of the basic domain of Tat did not affect the ability of PRMT6 to interact with Tat.
  
  
  RESULTS
  We next used the A549 human alveolar adenocarcinoma cell line, which naturally expresses undetectable levels of PRMT6, as a model for testing the effects of PRMT6 on Tat stability, transactivation, and HIV-1 replication. As previously observed, steady state levels and the protein half-life of Tat were increased by the ectopic expression of PRMT6. However, no down regulation of Tat transactivation function was observed, even with over 300-fold molar excess of PRMT6 plasmid. We also observed no negative effect on HIV-1 infectivity when A549 producer cells overexpressed PRMT6.
  
  
  CONCLUSIONS
  We show that PRMT6 requires the activation domain, but surprisingly not the basic domain, of Tat for protein interaction. This interaction between Tat and PRMT6 may impact upon pathogenic effects attributed to Tat during HIV-1 infection other than its function during transactivation.
authors.affiliation: Queensland Institute of Medical Research, Molecular Virology Laboratory, 300 Herston Road, Herston, Brisbane 4006, Australia.
authors.forename: Haran
authors.initials: H
authors.lastname: Sivakumaran
authors.forename: Min-Hsuan
authors.initials: MH
authors.lastname: Lin
authors.forename: Ann
authors.initials: A
authors.lastname: Apolloni
authors.forename: Vincent
authors.initials: V
authors.lastname: Cutillas
authors.forename: Hongping
authors.initials: H
authors.lastname: Jin
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Li
authors.forename: Ting
authors.initials: T
authors.lastname: Wei
authors.forename: David
authors.initials: D
authors.lastname: Harrich
mesh_terms: D002460:Cell Line; D004847:Epithelial Cells / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011484:Protein-Arginine N-Methyltransferases / Q000378:metabolism*; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; C447833:PRMT6 protein, human; D011484:Protein-Arginine N-Methyltransferases